1. Field of the Invention
This invention relates to a projection-printing apparatus for use in the manufacture of elements of semiconductor circuits such as IC, LSI, super-LSI, etc. More particularly this invention relates to a printing apparatus which uses an imaging optical system for forming the image of a part or all of a mask on a wafer and in which the mask and the wafer together are moved or only one of them is moved relative to the imaging optical system to thereby project the image of the mask upon the wafer.
2. Description of the Prior Art
The assignee of the present invention has already proposed a printing apparatus in which the image of a part of a mask is formed on a wafer and the mask is moved relative to an imaging optical system (Japanese Patent Application Laid-Open No. 53867/1979 laid open on Apr. 27, 1979). Also known is a so-called stepper projection-printing apparatus in which a reduced image of the whole of a mask is formed on a wafer and the mask is moved in stepwise fashion relative to the imaging optical system, whereby multiple mask images are printed on the wafer.
In such scanning type projection-printing apparatus, it is necessary to control a driven member with guide means.
For this purpose, for example, in the moving mechanism of the projection-printing apparatus of the aforementioned Japanese Patent Application Laid-open No. 53867/1979, a mask supporter and a wafer supporter integrally coupled together are movably supported on two guide rails and moved along these guide rails. Accordingly, when these guide rails are not accurately aligned or are not rectilinearly accurate, the mask and wafer are spatially inclined in two dimensions relative to the optical system and spatial deviation of the mask image occurs. Therefore, the accuracy of the rectilinearity of the two guide rails must be strictly controlled.
Also, even if the guide rails are manufactured with high precision, they may deviate from their original precise form with lapse of time.